I'm not really sure why this episode is listed as a sequel to season four, but nonetheless, I've watched it because of that fact. This episode isn't anything all that special, I will say, however, it does leave a nice feeling in your heart afterwards. Natsume's Book of Friends is brilliant at storytelling through these youkai and through Natsume, both outcasts in a sense. This specific story is a nice metaphor for humanity's ever-long search for something without knowing what it is they're searching for. Through this little episode, you get to see the creative way that very thing is talked about, and that's whatmakes this anime so great. It takes the most mundane things and adds a fantastical element to them to make it awe-inspiring to watch. Obviously, as this is an OVA, there isn't much by way of character development, but it's calming to just sit back and enjoy these characters in the wonderful environment that's been built for them. If you like the anime, this OVA is a good one to watch.